Accurate determination of microwave material permittivity and loss factor over the entire microwave regime and over the desired temperature range of operation are needed for accurate design, operation and evaluation of microwave components, circuits, antenna and systems. Microwave engineers can input such precise material parameters into currently available software programs to accurately model devices as functions of temperature. In this way, the number of iterations and time required to develop components, circuits, subsystems and systems that operate to the specified performance level and over the specified temperature range of operation can be reduced. Such efficient development, rather than development by trial and error, will lower component, circuit, subsystem and system cost.
U.S. Pat. No. 6,864,690, hereby incorporated by reference, discloses an open confocal resonator-based system that allows for the accurate determination of microwave dielectric properties at multiple (25 to 50) frequency points in the frequency range 15 to 50 GHz and over the temperature range −50 to 125° C. Precision micrometer drive units are provided to move the sample about a vertical axis, to tilt the sample, and to move the sample in X, Y and Z directions. The drive units are positioned on a bearing slide for ease of sample positioning into and out of the cavity. Selected drive units are controllable from a remote location so that the apparatus may be utilized in an environmental chamber whereby measurements may be accomplished without opening the chamber after each measurement. All components of the resonator system, positioning units, cables, etc. are chosen such that they are operable over the desired temperature range of operation. However, the disclosed system has some significant limitations. The lower frequency limit (cut-off) due to physical constraints of the cavity and sample size is limited by cross-sectional area of the microwave mode supported by the cavity, the mode becoming prohibitively large at lower frequencies.